The present invention relates to fuses and more particularly to riser pole fuses.
Riser pole fuses are large capacity fuses which are mounted on poles adjacent transformers, or other power line equipment which require separate power interruption protection. Such fuses are typically located in the power distribution lines at the top of twenty to forty foot poles. The fuses are located at numerous places throughout the power distribution system wherever line or power distribution component protection is required.
When a riser pole fuse opens, it interrupts the power distribution circuit at that point. Opening of the fuse can occur from natural events, such as lightning, or the touching of adjacent live wires from the effect of wind, or line surges caused by the failure of power distribution components.
One major problem associated with riser pole fuses is the identification of the location of a blown, or open fuse in the circuit. The fuse must be replaced in order to reconnect and reinstate that portion of the power distribution system protected by the open fuse into the main electrical distribution system. As the fuses are at the top of poles and several fuses may be located in an area where the power has been interrupted, it is often difficult to identify the open fuse and several fuses must be checked to determine which fuse has in fact opened.
One known method of identifying opened fuses is a colored button or spike, which pops out of a small aperture in one end ferrule of the fuse, to indicate that the fuse has opened. A button is attached to the fusing element of the fuse by a spring loaded ni-chrome wire, and when the fuse blows, the wire breaks and the button protrudes out the end ferrule of the fuse.
The major problem with the button indicator is visual identification. Although the line repair crew can view the fuse and therefore need not climb the pole to determine whether the fuse is opened in clear weather, in bad weather or at night it is difficult or impossible to see the button, rendering it virtually useless. Likewise, as the button is a stiff member which is recessed within the fuse, it has a limited length, i.e. it cannot exceed the length of the fuse and is commonly on the order of one to two inches. As a result, the repair crew must stand in direct visual alignment with the end of the fuse to see the button.
U.S. Pat. No. 891,323, Brown, discloses a blow indicator comprising an accordion shaped fan which flips out from the side of the fuse to indicate an open fuse. To view the fan, the fuse must be aligned such that the fan will eject from the side of the fuse exposed downward toward the repair personnel.
U.S. Pat. No. 817,959, Craft. discloses a spring mounted bar which flips up in the presence of an overcurrent.
U.S. Pat. No. 1,382,989, Lee, discloses a metal triangular flag which protrudes from a fuse box in the event of an overcurrent condition which opens the fuse.
U.S. Pat. No. 2,086,406, Dieffenbacher, discloses a fuse having a metal indicator which flips up to disclose an open fuse. Similar constructions are found in U.S. Pat. No. 2,239,903, Schultz. and 2,413,563, Humann.
The present invention overcomes the deficiencies of these prior art fuses.